Maybe the idea is crazy but here I go
Is possible (or anybody did it before) to use two Ardupilots working together?
One master and the other slave. If the master don´t works (instant) a transistor conection wake up the slave Ardupilot and it will take the control of the drone. The second unit is connect to a external safe battery and It can swap the control to Master unit or Slave makes a mandatory return to home to landing or continue working. This reduce much the crash probability, don´t you?
Excuse me for my poor english.